Along with advancement of semiconductor elements in terms of miniaturization, lower voltage operation, and higher integration, numerous types of system LSI and SoC (system on a chip) including a digital and an analog units based on CMOS (complementary metal oxide semiconductor) have been developed in recent years. A power amplifier is a key element in an analog unit based on the CMOS. As the MOS power amplifier, a power amplifier of a multi-finger gate structure, a power amplifier of a waffle gate structure using rectangular gates, and the like have heretofore been proposed.
However, the multi-finger gate structure has a problem that the size cannot be reduced due to an increase in the chip area. In the meantime, the multi-finger gate structure and the waffle gate structure have a problem that an influence of hot carriers generated in the structures cannot be suppressed.